3(х-1)+х=2х  

3х-3+х=2х

3х+х-2х=3

2х=3

х=2/3

  5(х+4)+х=6

5х+20+х=6

5х+х=6-20

6х=-14

х= -2 2/6= -2 1/3

3(х+4)=5х-7

3х+12=5х-7

3х-5х= -7-12

-2х= -19

х= 19/2 = 9,5

2(х-5)=7

2х-10=7

2х=7+10

2х=17

х=17/2=8,5

12+3(х-1)=0

12+3х-1 = 0

3х=1-12

3х= - 11

х= - 11/3 = - 3 2/3

3(х-7)-6х=--х

3х-21-6х= -х

3х-6х+х=21

-2х=21

х=- 21/2 = - 10,5

2(х+3/5) - х = 3 1/5

2х+ 6/5 - х = 3 1/5

2х - х = 3 1/5 - 6/5

х= 2